Connecting pressure
gauges:
Stoptheengine.Removetheservicevalveprotectivecaps.Connectthelowpres-
sure gauge to valve S and high pressure gauge to valve D.
Disconnecting gauges: Stop the engine. Unscrew rapidly the low pressure gauge. Run the air co nditioner
5---10 min and stop the engine. Unscrew rapidly the high pressure gauge.
Note! Refrigerant in the gauge hoses blows off. Use gloves and goggles when con-
necting and disconnecting gauges. Recap valves.
1147
Model Code Page
83. Air conditioner
1. 4. 1997
6000--8750 831 5
1. 1. 1994
2. Trouble shooting with pres-
sure gauges
System pressures depend directly on air pressure and tem-
perature. At outdoor temperature 20˚ --- 2 5 ˚C and at engine
revs 1500 r/min the low pressure varies between 50 ---300
kPa and the high pressure between 700 ---1400 kPa.The
pressure gauges are connected to the compressor service
valves: low pressure gauge to (S) and high pressure gauge
to (D). The service valves are different on the air conditioners
which have refrigerant R134a thus preventing mischarging
with freon R12.
Fault analysis and symptoms
a) Leaks in the system will lead to inadequate cooling and low
and high gauge readings will be too low.
b) If the system is under---charged, bubbles will be perma-
nently visible in the dehydrator sight glass and both gauge
readings will be low.
c) If the evaporator is dirty or an expansion valve is blocked
or frozen up, there will be a partial vacuum on the lowpressure
side and insufficient pressure on the high pressure side.
Low pressure too low High pressure normal
DS
d) An over---charged system, an expansion valve stuck open
or a clogged condenser will cause excessive pressure on the
low pressure side.
e)Acloggedcondenserandanover---chargedsystemwill
cause excessive pressure on the high pressure side.
Overcharge
Note! The correct refrigerant filling is 1,4 kg on Valmet
6000---8750 tractors.
In a correctly charged system, R12 discharged from the com-
pressor in the form of gas looses its excess heat, resulting
from compression in the first coil of the condenser and con-
denses to a liquid in the subsequent coils. B efore flowing to
the reservoir, this liquid is held in the last condenser coil. If the
system is over---charged, the liquid level builds up in the con-
denser, leaving fewer coils available to condense the gas.
Both temperature and pressure then build up, causing hoses
to burst in some cases.
Possible fault
Remedy
1. Expansion valve faulty.
2. Moisture in system caus-
ing icing in expansion valve
3. Expansion valve is
cloggedorevaporatordirty,
if low pressure gauge
shows underpressure.
4. Drier blocked (t empera-
ture difference on different
sides of blockage causes
icing in the drier when air
conditioner is functioning).
1. Change expansion valve.
2. Empty and flush the sys-
tem. Change the drier and
theexpansionvalveif
necessary.
3. Empty system and
change the expansion
valveandalsotheevapor-
ator and drier if necessary.
4. Empty system and
change the drier.
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